Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2001-05-25
2003-06-24
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C427S216000, C427S218000, C427S220000, C427S222000, C427S255600, C106S218000, C106S241000, C106S286100, C106S403000, C106S412000, C106S415000, C106S438000, C106S439000, C106S440000, C106S441000, C106S442000, C106S445000, C106S447000, C106S450000, C106S451000, C106S452000, C106S453000, C106S455000, C106S456000, C106S460000, C106S479000, C106S480000, C106S499000, C106S500000, C428S357000, C428S375000, C428S402000, C428S403000, C241S024250
Reexamination Certificate
active
06582506
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of pigmented coating materials. In particular, the present invention relates to pigment flakes having brilliant and highly reflective optical characteristics, to coating applications thereof, and to a method of making the pigment flakes using vapor deposition techniques to deposit a thin layer of colorant directly on a core material which is subsequently fractured to form discrete flakes.
BACKGROUND OF THE INVENTION
Colorants are well known classes of chemicals which are used to color or modify the hue of a substrate. Various forms of colorants have been used throughout human history. The term colorant includes, but is not limited to, organic and inorganic pigments, dyes, and combinations thereof. Metals are considered inorganic pigments; however, pure metals and alloys are frequently considered separately. The Colour Index International: Fourth Edition Online (Colour Index) is an internationally recognized registry of colorants, and is published jointly by the British-based Society of Dyers and Colourists and the American Association of Textile Chemists and Colorists. The Colour Index is found online at www.colour-index.org, and includes 800 color index classifications and a listing of thousands of pigment and dye products. The listings include chemical properties and manufacturers.
The fundamental difference between pigments and dyes is that dyes are soluble in the application medium while pigments are insoluble. Colorants, in general, are divided into appropriate hue groups, which include yellow, orange, red, violet, blue, green, brown and black in that order, additionally pigments further include the hue groups white and metals. Objects are colored if they selectively absorb and reflect incident light. Pure white reflects all light uniformly and pure black reflects no light. Pigments retain a crystal or particulate structure throughout the coloration process. Furthermore, pigments alter appearance by selective absorption and/or by scattering of light. Pigments are usually dispersed in vehicles or substrates for application, as for instance in the manufacture of inks, paints, plastics, or other polymeric materials. Dyes, on the other hand, are soluble, and the crystal structure of the chemical substance is typically destroyed, at least temporarily.
Pigmented coatings and pigment powders are well known. Pigment powders are composed of very small particles or flakes of organic or inorganic pigment. Particle shape is important in some applications. Needlelike particles apparently improve brushability and enhance adhesion, while platelike particles physically block out light and moisture thereby offering corrosion protection. A variety of particulate shapes are known, including needlelike, rodlike, spherical, cubic, small platelet and large platelet. Combinations of shapes may be present in single batches of pigment. Particle size is also an important consideration that influences the color strength, gloss, rheology, opacity and light fastness of pigment applications.
Pigmented coatings typically involve suspending a small amount of pigment powder in water or a volatile substance, applying the suspension to a substrate, and allowing the liquid in the suspension to evaporate thus covering the substrate with particles of pigment. U.S. Pat. No. 3,713,870 discloses a coating method for depositing metallic flakes on the surface of an object; the method involves suspending very thin, relatively small flakes in a volatile liquid, coating an object with the resulting suspension, and allowing the volatile liquid to evaporate resulting in the object having a thin, metallic coating held in place by intermolecular attraction. U.S. Pat. No. 4,003,872 describes a process whereby small flakes of metal and plastic particles are polished together to form a polished metal flake pigmented plastic powder product; upon application to a substrate, the plastic powder product is melted to form a smooth uniform film coating. Nearly all coatings require flakes of organic or inorganic pigment to provide the desired optical effect.
Generally, the amount of reflection a surface presents is directly proportional to the smoothness and regularity of the surface on the molecular level. Densely packed molecular surfaces, which are relatively unbroken having few apertures, breaks, depressions or prominences, are highly reflective. Light hitting a smooth and regular molecular surface reflects off the surface at highly uniform, discrete angles resulting in a brilliant and lustrous appearance analogous to smooth polished metals or mirrors. Light striking an irregular molecular surface is reflected at odd, nonuniform angles resulting in a dull appearance.
Most affordable pigments naturally have irregular shapes resulting in a dull, lusterless appearance. For example, the natural state of aluminum, an ingot, has a dull light-gray appearance. The molecules of aluminum naturally clump together in irregular patterns. A microscopic view would reveal jagged surfaces with crevices and protrusions. When aluminum is ground up and dispersed into a coating medium such as water or other solvent, and applied utilizing any conventional coating, printing or other technique, the resulting appearance is dull and gray. The natural states of nonmetallic inorganic and organic pigments are comparable. The appearances of other pigments in coating and printing applications having similar irregular shapes are the same. Carbon black, for example, has an irregular lumpy shape at the molecular level and a dull black appearance. When nonmetallic inorganic or organic pigments are fractured and utilized in coating, printing or other applications, the result is a flat nonreflective coloring.
Many techniques are utilized to improve the smoothness, gloss and brilliance of coatings containing pigmented powder. The first consideration is the smoothness and regularity of the article to be coated. Providing an initially smooth and regular surface is the first step in achieving a reflective, glossy coat. Other techniques involve grinding the pigment into very fine particles, integrating the particles into a coating composition, cross-linking the coating through energy infusion, and doctoring, calendering or embossing after the coating has been applied to the substrate. Additionally, extreme precision in the placement of pigment flakes in coating or printing applications may be used to assure that the pigment flakes present a smooth face so that the angles of reflection of the separate flakes are predominantly uniform. These techniques may be quite expensive and time consuming.
Dyes are inherently nonreflective. According to the Dyes and Toxicology Organization, which represents domestic dye manufacturers, dyes are defined as intensely colored or fluorescent organic substances which impart color to a substrate by selective absorption of light. To be reflective, dyes must be added to a reflective medium such as a glossy coating medium or the like.
Numerous methods have been developed to make fine thin flakes of metal for use as pigments. These metallic flakes have the disadvantage of bending, curling or breaking. Malformed metallic flakes have less than desirable optical qualities because they do not present a smooth surface. U.S. Pat. No. 4,321,087 issued to Levine et al. on Mar. 23, 1982 discloses a process for making metallic leafing pigments. The process therein involves a release coating continuously applied to at least one side of a carrier sheet. Metal vapor is condensed onto at least one surface of the release coating forming a thin metal film. The carrier sheet, the release coating and the thin metal film are then passed through a solvent system which releases most of the thin metal film into the solvent. The thin metal film is placed in a non-reactive liquid medium where it is fractured into finer pigment particles by vigorous stirring or ultrasonics The resulting metal flakes are concentrated and formulated into coating and printing compositions.
U.S. Pat. No. 5,718,753 b issued
Bell Mark L.
Hailey Patricia L.
Hampden Papers, Inc.
McCormick Paulding & Huber LLP
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