Patent Application
20070292608
The features and advantages of the present invention will be more readily understood, by those of ordinary skill in the art, from reading the following detailed description. It is to be appreciated those certain features of the invention, which are, for clarity, described above and below in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any sub-combination. In addition, references in the singular may also include the plural (for example, “a” and “an” may refer to one, or one or more) unless the context specifically states otherwise.
The use of numerical values in the various ranges specified in this application, unless expressly indicated otherwise, are stated as approximations as though the minimum and maximum values within the stated ranges were both preceded by the word “about.” In this manner, slight variations above and below the stated ranges can be used to achieve substantially the same results as values within the ranges. Also, the disclosure of these ranges is intended as a continuous range including every value between the minimum and maximum values.
All patents, patent applications and publications referred to herein are incorporated by reference in their entirety.
The invention is useful for matching paint and most particularly for matching paint on vehicles. “Vehicle” includes automobiles; light trucks; medium duty trucks; semi-trucks; tractors; motorcycles; trailers; ATVs (all terrain vehicles); pick-up trucks and includes automobile bodies, any and all items manufactured and painted by automobile sub-suppliers, frame rails, commercial trucks and truck bodies, including but not limited to beverage bodies, utility bodies, ready mix concrete delivery vehicle bodies, waste hauling vehicle bodies, and fire and emergency vehicle bodies, as well as any potential attachments or components to such truck bodies, buses, farm and construction equipment, truck caps and covers, commercial trailers, consumer trailers, recreational vehicles, including but not limited to, motor homes, campers, conversion vans, vans, pleasure vehicles, pleasure craft snow mobiles, all terrain vehicles, personal watercraft, motorcycles, boats, and aircraft. Also included are industrial and commercial new construction and maintenance thereof; cement and wood floors; walls of commercial and residential structures, such office buildings and homes; amusement park equipment; concrete surfaces, wood substrates, marine surfaces; outdoor structures, such as bridges, towers; coil coating; railroad vehicles; machinery; OEM tools; signage; fiberglass structures; sporting goods; and sporting equipment.
CIE L*, a*, b* color coordinate values, herein referred to as “L*, a*, b* color data values” are standard values read by conventional basic color measuring instruments, such as, a portable colorimeter as shown in U.S. Pat. No. 4,917,495 or a spectrophotometer from X Rite Incorporated, Grandeville, Mich., for example, an X Rite SP64 spectrophotometer.
The term “color data value” or “color data values” herein refers to a set of values used to describe a color specified by the CMC (Colour Measurement Committee of the Society of Dyers and Colourists (UK), R. McDonald, Acceptability and Perceptibility Decisions Using the CMC Color Difference Formula, J., Soc. Dyers and Colourists, June 1988 pages 31-37) or International Commission on Illumination, such as, but not limited to, CMC, CIE94, CIEDE2000, and CIELAB (also commonly referred to as L*,a*,b* or Lab). Color data values may also include values produced by other color measurement methods or instruments known to the industry, such as, but not limited to, (1) Hunter L, a, b, wherein L=lightness, a=green and red and b=blue and yellow; (2) CIELCH: a color standard developed from CIELAB; (3) XYZ tristimulus values; and (4) Yxy expression of the XYZ values. L*, a*, b* color data values produced by aforementioned portable calorimeters or spectrophotometers can be used in this invention.
“Color cluster” refers to a cluster of L*, a*, b* color data values taken from measurements of a group of vehicles of the same paint color.
“Centroid” means the center of a color cluster from which a paint formula is calculated via computer implementation, which is matchable by conventional spraying, blending and shading techniques to an original paint color that is within the color cluster.
“Cluster Analysis” is the procedure used to form clusters and determine the size (diameter) of the cluster and the relationship of one cluster to another cluster. Cluster analysis is more fully described in an article “Cluster Analysis”, a tutorial, by N. Bratchell, Chemometrics and Intelligent Laboratory Systems 6 (1989), 105-125, which is hereby incorporated by reference. Another useful reference is “Clustering Methods and their uses in Computational Chemistry” by Geoff M. Down and John M. Barnard, Reviews In Computational Chemistry 18, (2002), 1-40, which also is hereby incorporated by reference.
“Gamut” is the range of colors that can be reproduced in a specific color space or on a specific device.
“Gamut Visualizer” is an instrument that reproduces L*,a*,b* color data values visually on a screen and is utilized to show color clusters and is described in U.S. Patent Publication 2004/0100643 A1, published May 27, 2004, which is hereby incorporated by reference.
The color of the paint is described in L*, a* and b* values which are coordinates in visual uniform color space and are related to X, Y & Z tristimulus values by the following equations which have been specified by the International Committee of Illumination:
L* defines the lightness axis
L*=116(Y/Yo)1/3−16
a* defines the red green axis
a*=500[(X/Xo)1/3(Y/Yo)1/3]
b* defines the yellow blue axis
b*=200[(Y/Yo)1/3−(Z/Zo)1/3]
where
It is generally well accepted that the three-dimensional color space can be used to define colors in terms of certain color characteristics or color attributes. CIELAB, also commonly referred to as L*,a*,b* and Lab, is a uniform device that shows independent color space in which colors are located within a three-dimensional rectangular coordinate system. The three dimensions are lightness (L*), redness/greenness (a*) and yellowness/blueness (b*). In a typical three dimensional graph used to illustrate these color data values, the vertical axis which is L*, the black/white axis, represents a scale of luminous intensity or degree of lightness. The axis perpendicular to the plane of the graph or figure, the a* axis, is the red/green axis which represents a scale of red/green appearance. The horizontal axis is the b* axis which is the yellow/blue axis and represents a scale of yellow/blue appearance.
The information contained in the combination of a color's a*-b* axes position represents the chromatic attributes known as hue and saturation. The hue varies with the position about the L* axis and the chroma changes with the distance from the L* axis.
Chroma=C*=√{square root over (a*2+b*2)}
Hue=h=tan−1 (b*/a*);
this is referred to as the hue angle.
Therefore, a complete set or group of color attributes, or the attributes defining coordinates comprising lightness (L*), red/green (a*), and yellow/blue (b*) in the L*,a*,b* color space, fully defines a color point or locus in the color space. When generally used herein, the term “color” shall be understood to be fully defined by one or more complete sets or groups of color attributes or corresponding coordinates considering all three dimensions or axes in a three dimensional color space.
Color is usually judged versus a color standard, with color measurements expressed as a color difference versus that standard.
ΔL*=L*sample−L*standard
Δa*=a*sample−a*standard
Δb*=b*sample−b*standard
ΔC*=C*sample−C*standard
A total color difference is expressed as
ΔE*=√{square root over (ΔL*2+Δa*2+Δb*2)}
The hue difference is expressed as a metric hue difference rather than a hue angle difference
ΔH*=k√{square root over (ΔE*2−ΔL*2−ΔC*2)}
or ΔH*=k√{square root over (2(C*2C*b−a*sa*b−b*sb*b))}
Transformations of CIELAB space have been published in order to make it agree better with visual assessments. The general equation is
The CIE94 color space and a method described by Rodrigues et al (Rodrigues, A. B, J. and Locke, J. S., Proceedings of the 9th Congress of the International Colour Association, SPIE Vol. 4421 (2001), page 658-661) defines the parameters
SL=1.0 for solid colors
S
L=0.034L*; If L*≦29.4, SL=1.0 for gonioapparent colors
S
c=1+0.045C*ab
where C*ab=SQRT(C*standard.C*sample)
S
H=1+0.015C*ab
The parametric factors KL:KC:KH=1:1:1 are generally satisfactory
Other commonly used color spaces are CMC and CIEDE2000
Color can be further described at a variety of refection angles, L(θ), a(θ) and b(θ), where θ is the particular reflection angle as measured from the specular direction. Commercial multi-angle calorimeters and spectrophotometers are widely available and are useful in measuring the L*, a* and b* values at several angles in one reading. Instruments often allow 5-10 angles of measurement, including multiple angles of illumination. Preferably, the following angles are used: 15°, 45°, and 110° as measured from the specular angle when the color being matched contains metallic or pearlescent flakes. For solid colors, the 45° angle is sufficient, or even diffuse measurements, integrating the light reflected at all angles.
The aforementioned prior art methods for developing matching refinish paint formulations, e.g., using a spectrophotometer, color chips, alternate refinish color formulations, generally resulted in a large number of paint formulas that could be used and made it very difficult for a refinish operator to choose the closest color matching paint formula with any level of assurance that the paint could be colored matched. Often panel spray test runs were made and if a match could not be obtained, the formula was slightly adjusted or another formula chosen to provide a closer match.
The process of this invention by the use of color chips that are directly associated with centroids of color clusters that are developed to match original paints on vehicles allows a refinish operator to make a choice of a paint formula that has a high level of assurance that the color of the resulting refinish matching paint will be color matchable to the original paint using standard application techniques.
To implement the process of this invention for the development of color chips for refinish paint formulas, a color cluster database must be developed for a specific color of a vehicle. Since there are variations in color even from the same manufacturing facility and from different manufacturing facilities, color data values (CIE L*,a*,b* color data values) preferably is obtained for at least thirty vehicles from different locations and vehicles made at different times. Original paint color data values (CIE L*, a*, b* values) of each vehicle are obtained at multiple angle. Preferably 3 angles are used, 15°, 45° and 110°. For vehicles manufactured overseas, measurements are taken at entry ports, rail-heads and similar locations where there are large groups of vehicles assembled.
Via computer implementation, the color data is compared to and positioned in color clusters for the particular paint color that is to be matched and a paint formula of a refinish paint for the centroid of that color cluster is identified and developed in a laboratory. The refinish paint is formulated according to the formula for the centroid. This refinish paint is spray applied to form color chips either by the paint manufacturer or by an operator skilled in the art. The resulting paint chips are placed on or adjacent to the paint surface to be color matched and the operator visually selects the chip that provides the closest color match. The operator then spray applies the refinish paint corresponding to the selected color chip using standard spraying, blending and shading techniques to match the color of the undamaged original paint. For flake containing paints, visual comparison is usually required to determine that appearance of the flake, for example, color flop, flake sparkle and texture is acceptable. The applied refinish paint is subsequently dried and cured using standard techniques.
In determining the volume of a color cluster, all of the data points within the cluster will be color matched by conventional blending techniques using the formula of the centroid of the cluster. The cluster is mapped in multi-dimensional color space that allows for the three dimensions of color and the multiple angles at which it is measured. The use of visually uniform color space, such as, CIE94 allows the three dimensions of color space to be weighted equally. It may be desirable to weight the measurement angles for customer preference in determining the volume of the color cluster for blendable color matching paint. The multiple angles of measurement are weighted to allow for customer preferences. For example, when approaching a vehicle and judging color acceptability of a paint repair, especially on a horizontal surface, the 110° angle is the most noticeable and should be weighted the highest. On the other hand, some customers place a greater emphasis in color match when viewed very close to the mirror or specular angle of reflection of the light source. In such a case, the 15° angle should be weighted higher.
Box 32 of
A Gamut Visualizer can be used to display the aforementioned data.
The computer program utilizes Cluster Analysis techniques to determine the size of the color cluster, the number of clusters, the distance between clusters and the centroid of each cluster.
Cluster Analysis techniques are described in detail in an article “Cluster Analysis” by N. Bratchell, and “Clustering Methods and their uses in Computational Chemistry” by Geoff M. Down, and John M. Barnard, supra. From these articles, those skilled in the art can readily determine useful color clustering techniques used for determining color clusters, the size and diameter of color clusters, the distance between color clusters and the centroid of each color cluster.
Box 35 of
When new vehicle colors are introduced, refinish paint suppliers receive color standards. These standards can be matched through visual methods or commercial computer color matching programs, such as, Datamatch® (Datacolor, Lawrenceville, N.J.). The color difference between the color data values of the centroid and this first match can then be adjusted using the same commercial software or methods such as disclosed in Armstrong et al, U.S. Pat. No. 3,690,771 issued Sep. 12, 1972 which is hereby incorporated by reference. Other commercially available color shading programs are available from GretagMacBeth LLC New Windsor, N.Y., USA.
The important point of the novel process of this invention is that if an original paint color falls within a color cluster, the paint formula directly derived from the centroid of the color cluster will be matchable to the original paint of the vehicle being refinished by a skilled technician using standard spraying, blending and shading techniques.
The novel process of this invention can be used to match finishes on vehicles having a standard pigmented mono coats, clearcoat/pigmented basecoat or tri-coat finishes and can be used to match solid color as well as coatings containing metallic flake and or special effect imparting pigments.
The present invention is further defined in the following Example. It should be understood that this Examples is provided by way of illustration only. From the above discussion and these Examples, one skilled in the art can ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various uses and conditions. As a result, the present invention is not limited by the illustrative example set forth herein below, but rather is defined by the claims contained herein below
The following Example illustrates the invention.
L*,a*,b* color data values were determined for several vehicles coated with Light Sapphire Blue paint Ford 6993. L*,a*,b* color data values were measured using an X-Rite MA 90B Metallic Field Colorimeter made by X-Rite Incorporated, Grandville, Mich. Color data values were taken on the hood and on the driver's side door of each vehicle. L*,a*,b* color data values were recorded at these two locations on the vehicle at 15°, 45° and 110° viewing angles
All of the L* a* b* color data values determined above for each of the angles 15°, 45° and 110° were evaluated using cluster analysis techniques described in “Cluster Analysis” and “Clustering Methods and their uses in Computational Chemistry” by Geoff M. Down, and John M. Barnard, supra, whereby a color cluster diameter and distance between color clusters was set and a centroid was determined for each color cluster. A centroid was determined for each of the two optimized color clusters and designated as Alternate A and Alternate B. The L*, a*, b* values for these centroids at each angle are shown in the table below. A refinish paint formula was determined to match each of these centroids and color chips were prepared by spraying these paints onto a conventional substrate used to form color chips and dried and cured using conventional techniques well known to those skilled in the art. These chips were positioned adjacent to the original paint on the vehicle to be repaired. Visually comparing them to the vehicle, Alternate B appeared darker, greener and more blue compared to the vehicle at most viewing angles. It also appeared too red compared to the vehicle when viewed at grazing angles, close to 110 degrees. Alternate A appeared to be a good color match and was selected to repair the vehicle. Once painted, the repair area was not distinguishable from the rest of the vehicle because the repair paint was a good color match.
The original color of the vehicle was measured for verification. In Table 1 below, the L*, a*, b* readings at the three angles are shown. Tables 2 and 3 show the L*, a*, b* values for Alternate Paints A and B and the difference between these values and the values of the original paint of Table 1. These calculated color differences for the two alternates paints versus the original paint of the vehicle are in agreement with the visual assessments above, i.e., Alternate Paint A provided the better color match. This measurement was only for verification and is not necessary to practice this invention.
This application claims the benefit of U.S. Provisional Application Ser. No. 60/814,116 filed on Jun. 16, 2006 which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60814116 | Jun 2006 | US |
