Note: Descriptions are shown in the official language in which they were submitted.
HW/P-20913/A/CGC 1865 CA 02208119 1997-06-19
Finishes containing light interference pigments
This application relates to a process for achieving unique polychromism effects in
automotive finishes by applying a two-coat or three-coat automotive finish to a substrate
and achieving polychromism in the finish by incorporating an opaque, light interference
pigment into the topcoat or a midcoat, which is applied over a colored basecoat, at a
pigment to binder ratio of from 0.001/100 to 7/100.
Finishes that show significant contrast in color and darkness depending upon the viewing
angle, often referred to as "polychromism", "flop" or "travel", are currently considered highly
desirable for automotive finishes. In general, flop effects in automotive finishes are
currently achieved by use of a two coat system using a basecoat and a clear topcoat,
wherein the basecoat contains a combination of a transparent organic and/or inorganic
pigment with a metal, like aluminum, or a pearlescent, coated mica pigment.
Recently, a new class of opaque, light interference or optically-variable pigments was
described, for example, in U.S. Patent Nos. 4,879,140, 5,059,245, 4,705,300, 5,281,480,
4,434,010, 4,779,898, 4,838,648, 4,390,866, 5,135,812, 5,171,363, 5,214,530, 5,522,923,
5,527,848, 4,705,356, and US 5,607,504 which are here incorporated by reference.
Generally, these publications describe pigments prepared by stacking a transparent
dielectric layer and semitransparent (partially reflecting) layer on one or both sides of a
reflecting or opaque material to form a layered material having the structure
M,/D/M2 or M1/D/M2/D/M1
where M2 is an opaque layer, D is a dielectric material and M, is a semitransparent layer.
Generally, the color and degree of polychromism are controlled mainly by the thickness and
identity of the dielectric layer, which influences the interference between the light reflected
by the semitransparent layer and that reflected by the opaque layer.
In general, such light interference pigments are described as being produced either by
plasma vapor deposition of the layers under high vacuum, or by chemical deposition.
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U.S. Patent No.5,437,931 discloses that some benefits are derived by protecting the Ml
semitransparent layer with another layer of dielectric material, D', to form a layered material
having the structure
D'/M,/D/M2 or D'/M1/D/M2/D/M,/D'
This complicated array of layers can be extended even further.
When used in the waterborne basecoats commonly used in the automotive field, metal
containing pigments, such as the opaque interference pigments described above, undergo
corrosion or oxidation in contact with water, causing undesirable color shifts. U.S. Patent
No.5,527,848 describes a method to protect the opaque interference pigments fromcorrosion by outside influences, like water in a water-based paint system, by partial
oxidation of the metals contained in the pigment.
EP 668,329 and EP 571,836 disclose similar opaque interference pigments which are
produced by chemical means whereby aluminum flakes are coated with the dielectric SiO2
precipitated by hydrolysis of tetraalkoxy silane followed by deposition of a semitransparent
metallic layer such as molybdenum, chromium, iron etc. by decomposition of the
corresponding hexa or penta carbonyl compound. EP 579,091 describes another variation
of this approach whereby the dielectric layer is treated with molybdenum which is
subsequently oxidized to its oxide and the latter converted to MoS2 by treatment with H2S.
EP 690,105 further discloses that the semitransparent layer can be converted to its nitride
by contact with ammonia. These pigments also show strong polychromism and are very
opaque and chemically stable.
In this application, interference pigments composed of a light interference layer or light
interference layers and an opaque layer, such as those described above wherein a light
interference layer consisting of the transparent dielectric material and semitransparent layer
is applied to one or both sides of an opaque layer, are referred to as opaque interference
pigments in order to distinguish them from metal-oxide coated mica pigments, and the like,
which have been used in automotive finishes, in combination with a transparent pigment, for
some time. The interference layer acts to generate color and polychromism by causing
interference between light reflected from different surfaces, for example the
semitransparent and opaque layer surfaces, within the light interference layer.
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Opaque interference pigments provide remarkable contrast depending upon the angle of
viewing when used in coatings, yet are very opaque, producing saturated colors. This is an
oxymoron in terms of conventional pigment technology with oxide-coated mica pigments,
which are typically combined with a transparent organic and/or inorganic pigment to achieve
the desired pearlescent effects. Compared with conventional finishes containing an oxide-
coated mica in combination with a transparent pigment, finishes pigmented with an opaque
interference pigment provide unique optical effects, depending upon the viewing angle, not
attainable with oxide-coated micas, and excellent outdoor durability. In addition, the
opaque light interference pigments are incorporated into a paint vehicle by a simple mixing
step, often referred to as stir-in pigments in the automotive industry, which does not require
an intense dispersion step; whereas the transparent pigments used in combination with an
oxide-coated mica or aluminum flakes generally require intense dispersion steps, which add
considerably to cost, for incorporation into a paint vehicle due to its high surface area, and
therefore, high degree of aggregation.
The opaque interference pigments are used in paints, inks and plastics. In inks they are
used primarily to prevent counterfeiting of currency and other legal documents. The use of
opaque interference pigments in two-coat automotive finishes has been described. To
impart color and the metallic pearlescent effect to coatings, particularly automotive coatings,
significant quantities of the opaque interference pigments have been incorporated in the
colored basecoat of a basecoaVclearcoat finish. Such high pigment to binder ratios are
necessary to have a basecoat which provides complete hiding. However, the high cost of
the opaque interference pigments renders the use of finishes having pigmenVbinder ratios
in the appropriate range too expensive for normal use.
These publications do not disclose that the opaque interference pigment could beincorporated into a midcoat or clearcoat applied over an opaque black, white or colored
basecoat at a much lower pigment to binder ratio to achieve remarkable polychromism
effects in automotive finishes of widely varying color. In this application, the expressions
"colored basecoat" and "colored pigment" are intended to include black and white basecoats
or pigments.
It has now been discovered that the amount of the opaque interference pigment required to
obtain unusual visual effects is drastically reduced (thus reducing cost), while significantly
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expanding the available color palette, by depositing onto a substrate a three-coat finish
comprising a first coating containing an opaque white, black or colored pigment to achieve
total hiding, applying a second coating (midcoat) which contains the opaque interference
pigment over the first coat, followed by a conventional clearcoat. The first coating is applied
onto the primer, or it can serve as a colored primer. The second coat contains a minor
quantity of the opaque interference pigment where the pigmenVbinder ratio ranges from
0.001/100 up to 7/100 at a thickness from 8 to 40 ~Im. The second coating does not
completely hide the first coating. Thus, the amount of opaque interference pigment applied
onto the substrate is dramatically reduced, yet the coated substrate shows unique optical
effects resulting from the presence of the opaque interference pigment.
In a further preferred modification, the substrate is finished with a basecoaVclearcoat finish
wherein the clear topcoat having a thickness in the range from 25 to 75 llm is tinted with the
opaque interference pigment and applied directly over an opaque black, white or colored
basecoat, which in turn is applied onto the primer or which itself serves as a colored primer.
In this modification, the midcoat is eliminated, which further reduces cost, while imparting
the desired aesthetic effects.
Since the interference pigments utilized according to the present invention are opaque, they
are necessarily used in small concentrations to allow the colored basecoat to show through
in both the two-coat and three-coat finishing systems described above. Thus, both the two-
coat and three-coat finishes vary in color from yellow to orange to red to violet, blue and
green, and have a high degree of polychromism.
Compared to the clearcoaVbasecoat technology used with oxide-coated mica pigments, the
inventive finishes provide for cost-effective, novel effects, such as remarkablepolychromism, without the requirement of using a transparent organic and/or inorganic
pigment. Eliminating the transparent pigment drastically reduces rheological problems in
paint, thereby decreasing requirements for solvents that lead to environmental pollution.
Furthermore, transparent pigments require expensive dispersion processes to break up
aggregates and agglomerates formed during their manufacture. The invention eliminates
the need for this expensive, time-consuming dispersion process by using an opaque
pigment in the basecoat which is typically more easily dispersed than a transparent pigment
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and presents relatively fewer rheological problems. In addition, the invention produces
waterborne and solventborne finishes which generally have improved light and
weatherfastness compared with finishes containing a transparent pigment.
In addition, opaque interference pigments used according to the present process do not
require a treatment, such as that described in U.S. Patent No. 5,527,848, in order to
prevent corrosion of the metal layers when used with waterborne basecoats.
The present invention relates to a process for coating a substrate, which process
comprises:
(a) applying a first coating to the substrate, which first coating comprises an effective
pigmenting amount of an opaque pigment;
(b) applying a second coating over the first coating, which second coating comprises an
effective polychromism-producing amount of an opaque interference pigment, but does not
completely hide the first coating.
In particular, the present invention relates to a process which is a three-coat process
wherein a clear topcoat is applied over the second coating, and to a two-coat process
wherein the second coating is a tinted clearcoat (tinted topcoat), meaning that the opaque
interference pigment is dispersed in the topcoat.
The substrate that is coated according to the present process is not critical to the
applicability of the inventive process. However, since the inventive process is primarily
intended to be utilized as a finishing process for transportation equipment, the more
important substrates are materials utilized in the bodies of automobiles, bicycles,
motorcycles, vans, trucks, or other vehicles, especially metals, such as steel, iron and
aluminum, and plastics, such as thermoplastics, like polycarbonates, polyacrylates and
especially thermoplastic polyolefins.
The first coating is applied to a substrate which has been coated with a primer coating, or is
applied directly to the substrate as a primer coating. Since the first coating comprises an
opaque pigment, it is applied to completely hide the substrate, whether primed or not. In
general, the first coating contains an effective hiding amount of an opaque pigment.
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The first coating contains an opaque pigment. In this application, the expression "opaque
pigment" means a pigment composed of particles that are large enough to provide good
hiding and a high degree of light scattering. Generally, opacity is a function of particle size
with larger particle size pigments having greater opacity. The maximum opacity occurs with
particles having a size which is approximately half the wavelength of maximum absorption.
The opaque pigment utilized in the first coating is an opaque inorganic pigment or an
opaque quinacridone, 1,4-diketo-3,6-diarylpyrrolo[3,4-c]pyrrole, azo, azomethine, methine,
anthraquinone, phthalocyanine, perinone, perylene, thioindigo, iminoisoindoline,iminoisoindolinone, flavanthrone, indanthrone, anthrapyrimidine and quinophthalone
pigment, or a combination thereof. Preferably, the opaque pigment utilized in the first
coating is an inorganic pigment selected from carbon black, iron oxide, titanium dioxide,
bismuth vanadate, nickel titanate and chromium titarlate or an organic pigment which is a
quinacridone, 1,4-diketo-3,6-diarylpyrrolo[3,4-c]pyrrole, azo, phthalocyanine,
iminoisoindoline, iminoisoindolinone or indanthrone pigment, or a combination thereof.
The phthalocyanine pigments are generally copper phthalocyanine blue and green which
are especially applied as a mixture with titanium dioxide, for example a 50/50 mixture, in
order to hide the substrate.
A black basecoat provides particularly attractive finishes according to the inventive process.
Ordinary gray primers, which are normally composed of a mixture of titanium dioxide and
carbon black, are also useful as the basecoat.
In the inventive process, the second coating comprises an opaque interference pigment.
Opaque interference pigments useful in the inventive process generally consist of an
opaque layer which is covered by one or more light interference layers which act to reflect
incoming light from different points within the interference layer to create light interference,
resulting in color and polychromism.
The opaque interference pigment is advantageously an interference pigment which
essentially consists of flakes of the structure M1/D/M2 or M1/D/M2/D/M1 wherein M2 is an
opaque layer which is coated on one or both sides with a transparent dielectric layer, D,
which in turn is coated with a semitransparent layer, M,. Such or similar opaqueinterference pigments are described, for example, in U.S. Patent Nos. 4,879,140,
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5,059,245, 4,705,300, 5,281,480, 4,434,010, 4,779,898, 4,838,648, 4,390,866, 5,135,812,
5,171,363,5,214,530, 5,522,923 and 4,705,356. Interference pigments of the abovestructure which are coated with one or more additional dielectric layers or semitransparent
layers, or both, such as is described in U.S. Patent No. 5,437,931, also have utility in the
inventive process.
In general, M2 is an opaque metal layer, especially an opaque aluminum layer.
Since M2 must be completely opaque, having a light transmitance less than about 0.1% at
550nm, it generally must have a thickness of greater than 30 nm, especially if it is
composed of aluminum. Preferably, the opaque layer is a metal layer, especially an
aluminum layar, having a thickness of from 30 to 90 nm, preferably from 30 to 70 nm, most
preferably about 50 nm.
The dielectric layer, D, is any material which is transparent at visible wavelengths having a
dielectric constant preferably less than 1.70 (air=1), most preferably less than about 1.65.
The optical thickness (geometric thickness x refractive index) of the dielectric layer is
adjusted based on well-known optical principles to give rise to any desired interference
color. Materials that are especially useful as the dielectric layer include MgF2, SiO2 and
Al2O3, especially MgF2 and SiO2.
M, is a semitransparent layer. In general, M1 is a metallic layer which has a transmitance of
from about 30% to 40% at 550 nm. However, the transmitance requirement changes with
wavelength, with 50% transmitance being the usual target. Preferably, M, is composed of a
metal, such as chromium, molybdenum, tungsten or iron.
In order to practice the present invention, it is important that the second coating does not
completely hide the first coating. Thus, at least some of the color of the first coating shows
through the second coating.
The second coating is preferably a solvent-based coating. However, if the opaqueinterference pigment is treated to prevent corrosion of the metal opaque layer, and/or if the
pigment is not adversely affected by contact with water, the second coating can be a water-
based coating in the inventive process.
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ln general, the three-coat inventive process produces a coating showing a high degree of
polychromism when the second coating has a thickness in the range from 8 to 40 llm,
preferably 10 to 20,um, most preferably about 15 ~lm and contains the opaque interference
pigment at a pigment to binder ratio of from 0.001/100 to 7/100, preferably at a pigment to
binder ratio of from 0.001/100 to 3/100, most preferably at a pigment to binder ratio of
0.001/100 to 2/100. Other useful ranges for the pigment to binder ratio of the midcoat
include those having a lower limit of from 0.01/100 or 0.10/100 and an upper limit of 2/100,
3/100,5/100 or 7/100.
In general, the two-coat inventive process produces a coating showing a high degree of
polychromism when the second coating, which is equivalent to the topcoat in a conventional
automotive finish, has a thickness in the range from 25 to 75,um, preferably 40 to 65 llm,
most preferably about 50 ~lm and contains the opaque interference pigment at a pigment to
binder ratio of from 0 001/100 to 7/100, preferably 0.001/100 to 5/100, more preferably at a
pigment to binder ratio of from 0.001/100 to 3/100, most preferably at a pigment to binder
ratio of 0.001/100 to 2/100. Other useful ranges for the pigment to binder ratio of the tinted
topcoat include those having a lower limit of from 0.01/100 or 0.10/100 and an upper limit
of 2/100, 3/100, 5/100 or 7/100. Usually the gloss of the final finish is related to the particle
size of the opaque interference pigment, with smaller particle size pigments typically
producing high gloss and distinctness of image finishes.
In general, in the inventive processes, the first coating is applied at a rate which totally hides
the substrate, preferably to a thickness in the range from 10 to 50 ~lm, usually about 25 ~,lm.
In the three-coat process, the clearcoat generally has a thickness in the range from 25 to
100 ~m, usually about 50 ~Im.
Neither of the first or second coatings normally comprises a transparent pigment. However,
it may be possible to include a small amount of a transparent pigment in the second layer.
The expression "transparent pigment" is a term of art which is familiar to those in the
pigments industry. In general, it refers to a pigment which fails to hide at normal application
rates due to its small particle size, which minimizes light scattering. Assuming effective
dispersion, it is expected that pigments of smaller particle size will be more transparent than
the corresponding larger particle size pigment.
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The present invention further relates to a substrate which is coated by the inventive
process. Thus, the present invention also includes a coated substrate comprising a first
coating and a second coating wherein the first coating comprises an effective pigmenting
amount of an opaque pigment; and the second coating comprises an effective
polychromism-(or flop-)producing amount of an interference pigment, wherein the second
coating does not completely hide the first coating. If the substrate is coated by the inventive
three coat process, the second coating is located between the first coating and a
transparent topcoat.
All of the discussion above relating to the process also defines the finishes on the inventive
coated substrates.
The inventive coated substrate is preferably a transportation vehicle, such as an
automobile, bicycle, motorcycle, van, truck or boat.
The present invention also relates to a coating composition that is useful as the second
coating in the inventive process. Thus, the present invention relates to a coating
composition which comprises a solvent, like water or preferably an organic solvent, a binder
and an opaque interference pigment at a pigment to binder ratio less than 7/100, preferably
less than 5/100, more preferably less than 3/100, most preferably less than 2/100, for
example in the range from 0.001/100 up to, but not including, 7/100, preferably from
0.001/100 to 5/100, more preferably in the range from 0.001/100 up to, but not including,
3/100, most preferably in the range from 0.001/100 to 2/100. It is preferred that the
pigmenVbinder ratio be as low as needed to achieve the desired finish characteristics.
Preferably, the binder is a heat or light curable high-molecular-weight organic material that
is conventionally utilized for the solvent-based clear topcoat in basecoaVclearcoat
automotive finishes. In general, such high-molecular-weight organic materials include
polyacrylics, polymethacrylics, polyesters, polyurethanes and copolymers thereof.
Preferred coating compositions include those that contain from 40 to 80 percent by weight
of the high-molecular-weight organic material and an opaque interference pigment at a
pigment to binder ratio of from 0.001/100 to 7/100, preferably 0.001/100 to 5/100, more
preferably at a pigment to binder ratio of from 0.001/100 to 3/100, most preferably at a
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pigment to binder ratio of 0.001/100 to 2/100. Normally, the coating compositions also
contain other ingredients such as stabilizers, including UV absorbers and hindered amine
light stabilizers, dispersants, wetting agents, anti-settling agents and the like.
In general, the coating compositions of the present invention are useful as a tinted clearcoat
automotive finish. The coating compositions of the present invention do not include ink
compositions which generally have a higher pigment to binder ratio.
The following examples illustrate, but do not limit, the present invention. All parts are parts
by weight unless otherwise specified. The pigments utilized for the basecoats are identified
by the designation given in the Color Index, which is published by jointly by the Society of
Dyers and Colourists and the American Association of Textile Chemists and Colorists.
All reflectance spectra are taken from painted panels using an MAG8 Multiple Angle
Spectrophotometer (available from X-RITE of Grandville Ml). Reflectance spectra are
obtained under D65 normal light illumination under angles away from the gloss angle (90~
off the illumination source). The measured values are referenced to a white diffuse
reference standard.
Examples 1-3
The following describes the incorporation of several pigment types into a three coat
automotive system.
Basecoats - Millbase Formulations
1A. Millbase Formulation for Pigment Red 254 and Pigment Violet 19
A vessel is charged with 46.2 grams of acrylourethane resin (68% solids), 25.2 grams
polymeric dispersant (55% solids) and 46.2 grams of aromatic hydrocarbon solvent(Solvesso 100). 47.4 grams of pigment and 980 grams of 4mm diameter steel rods are
added. The mixture is milled for 48 hours on a roller mill at 100 rpm. The resulting millbase
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contains 28% pigment with a pigmenVbinder ratio of 100/100 and a total non-volatile
content of 56.0%.
1 B. Millbase Formulation for Other Pigments
A vessel is charged with 38.8 grams of acrylourethane resin and 113.0 grams of aromatic
hydrocarbon solvent (Solvesso 100). 13.2 grams of pigment (Pigment Black 6, Pigment
Yellow 110, Pigment Yellow 139, Pigment Blue 15.2, Pigment Green 7) and 980 grams of
4mm diameter steel rods or 1,27 cm (1/2") ceramic balls (PY110, PY139) are added. The
mixture is milled for 48 hours on a roller mill at 100 rpm. The millbase contains 8.0%
pigment with a pigmenVbinder ratio 50/100 and a total non-volatile content of 24.0%.
1C. Milling Formulation for Pigment Yellow 184
A vessel is charged with 35.3 grams acrylourethane resin, 63.75 grams of aromatic
hydrocarbon solvent (Solvesso 100). 66 grams of pigment and 800 grams of 1,27 cm (1/2")
ceramic balls are added. The mixture is milled for 24 hours on a roller mill. The millbase
contains 40% pigment with a pigmenVbinder ratio of 277/100 and a total non-volatile
content of 54.5%.
1 D. Titanium Dioxide Millbase Formation
A TiO2 millbase is prepared by mixing the following ingredients:
604.1 grams of a TiO2 pigment (DuPont R-960)
129.8 grams of acrylourethane resin, and,
161.1 grams of aromatic hydrocarbon solvent (Solvesso 100)
One pint of 1,27 cm (1/2") ceramic balls are added. The millbase is dispersed for 24 hours
on a roller mill. The "TiO2" dispersion contains 67.5% pigment with a total non-volatile
content of 77.4%.
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Basecoats - Basecoat Formulations
2A. Basecoat Formulation for PR 254 and PV 19
30.2 grams of millbase prepared according to Example 1A, 20.3 grams of a clear solids
solution (48.1% solids) containing a melamine resin catalyst, non-aqueous dispersion resin
and a UV absorber, and 49.5 grams of a balancing solid color solution (58.0% solids)
containing a polyester urethane resin and solvent are mixed and diluted with a solvent
mixture containing 76 parts xylene, 21 parts butanol and 3 parts methanol to a spray
viscosity of 20-22 seconds measured by a #2 Fisher Cup.
2B. Basecoat Formulation for Other Pigments
64.3 grams of millbase prepared according to Example 1 B, 24.7 grams of clear so~ids
solution containing a melamine resin catalyst, non-aqueous dispersion of resin and a UV
absorber and 11.0 grams of a balancing solid color solution described above containing a
polyester urethane resin are mixed and diluted with a solvent mixture containing 76 parts
xylene, 21 parts butanol and 3 parts methanol to a spray viscosity of 20-22 seconds
measured by a #2 Fisher Cup.
2C. Basecoat Formulation for PY184
66.7 grams of the millbase described in Example 1 C,10.0 grams of clear solids solution,
and 23.3 grams of a balancing solid color solution containing a polyester urethane resin are
mixed and diluted with a solvent mixture containing 76 parts xylene, 21 parts butanol and 3
parts methanol to a spray viscosity of 20-22 seconds measured by a #2 Fisher Cup.
2D. 50/50 Tint Basecoat Formulation for PB 15.2 and PG7
A 50/50 tint shade is prepared by mixing the following ingredients: 57.7 grams of millbase
described in 1 B, 8.6 grams of TiO2 dispersion described in 1 C, 22.7 grams of clear solids
solution and 10.0 grams of a balancing solid color solution described in 2A are mixed and
diluted as above.
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2E. Midcoat Formulations
The opaque interference pigments of the structure MJD/M2/D/M1 of the color described
below are formulated into midcoat formulations according to the recipes that follow. The
color of the pigment is controlled by varying the thickness of the dielectric layers.
Interference Pigment Color Shade
Greenish Gold to Silver
Yellowish Gold to Silver
Blue to Red
Red to Gold
These pigments are incorporated into several different midcoats by mixing pigment and
paint vehicle on a laboratory mixer.
Each midcoat has the following formula:
Midcoat Pigment/Binder Composition
0.0015/100 100 grams of clearcoat (60% solids) +
0.0009 grams pigment
0.015/100 100 grams of clearcoat (60% solids) +
0.009 grams pigment
0.15/100 100 grams of clearcoat (60% solids) +
0.09 grams pigment
1.5/100 100 grams of clearcoat (60% solids) +
0.9 grams pigment
3/100 100 grams of clearcoat (60% solids) +
1.80 grams of pigment
5/100 100 grams of clearcoat (60% solids) +
3.0 grams of pigment
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3A. Masstone and Tint Application
One of the basecoat formulations prepared according to Examples 2A-2D is sprayed onto a
panel twice in a 90 second interval as a basecoat. After 60 minutes flash time, a midcoat
formulation according to Example 2E is sprayed twice at 90 second intervals onto the
basecoat. After an additional 60 minute flash time, a clearcoat resin solution is applied and
flashed for 60 minutes. The system is baked in an oven at 128~C (265~F) for 30 minutes.
Typical dry film thicknesses of each coat in this tri-coat system are as follows:
Basecoat = 10-50 microns, preferably 20-40 microns
Midcoat = 8-40 microns, preferably 10-20 microns
Clearcoat = 25-75 microns, preferably 40-65 microns
The following table summarizes the colors that are obtained using various midcoaVbasecoat
combinations at pigment to binder ratios of 1.5/100.
Midcoat Basecoat Reflectance at an Angle of 25~
Pigment Pigment From the GlossAngle
L A B
Greenish GoldPY 184 68.7 -6.0 67.7
to Silver
Greenish GoldPY 110 52.7 19.9 55.6
to Silver
Greenish GoldPG 7 ~ TiO2 65.7 -14.9 42.3
to Silver (50/50)
Greenish Gold PB6 60.2 -2.5 43.0
to Silver
Yellowish GoldPY 184 75.2 -2.0 80.0
to Silver
Yellowish GoldPY 139 59.8 29.1 79.1
to Silver
Yellowish GoldPB 6 28.3 11.7 31.1
to Silver
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Yellowish GoldPY 110 53.4 30.0 70.2
to Silver
Blue to Red PV 19 26.0 35.2 -17.3
Blue to Red PB 6 19.3 14.8 -28.7
Blue to RedPB 15.3 & TiO2 28.8 -3.2 -35.7
(50/50)
Red to Gold PV 19 46.5 37.7 44.9
Redto Gold PR254 39.2 49.9 48.0
Red to Gold PB 6 44.4 33.3 42.9
The primary color of the finish is controlled by the identity of the pigment utilized in the
basecoat and the midcoat. The degree of polychromism is controlled by the pigmenV
binder ratio of the opaque interference pigment in the midcoat and the thickness of the
midcoat. In each instance, the finished panel shows polychromism even at a pigment to
binder ratio of 0.0015/100.
Example 4. Two Coat Finish
4A. Tinted Clearcoat Formulation
The red to gold opaque interference pigment described in Example 2E is incorporated into
four clearcoat formulations to yield tinted clearcoat formulations having pigment to binder
ratios of 0.0015/100, 0.015/100,1.5/100 and 5/100 by mixing the pigment and clearcoat on
a laboratory mixer in the amounts described below. The clearcoat is a conventional
automotive formulation composed of a mixture of acrylic resins (60% solids) in a blend of
ester and hydrocarbon solvents which contains 3.9% of stabilizer (UV absorber/hindered
amine light stabilizer).
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.
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Tinted Clearcoat PigmenVBinder Ratio Composition
(1) 0.0015/100 100g of clearcoat (60% solids)
+ 0.0009g pigment
(2) 0.15/100 100g of clearcoat (60% solids)
+0.09g of pigment
(3) 1.5/100 100g of clearcoat (60% solids)
+ 0.9g of pigment
(4) 5/100 100g of clearcoat (60% solids)
+ 3.0g of pigment
4B. Basecoat and Tinted Clear Application
One of the basecoat formulations described in Examples 2A (Pigment Violet 19) and 2B
(Pigment Black 6) is sprayed onto a panel twice in a 90 second interval as a basecoat.
After a 60 minute flash time, one of the tinted clearcoat formulations described in Example
4A is sprayed four times at 90 second intervals onto the basecoat. The sprayed panel is
then "flashed" for 60 minutes. The two-coat panel is then baked in an oven at 265~F for 30
minutes. Typically, the dry basecoat has a thickness of about 25,um. The dry tinted
clearcoat film typically has a thickness of about 50 ~lm.
Each of the finishes shows polychromism. The panels with PV 19 as basecoat and the red
to gold interference pigment in the topcoat have a distinct polychromism and a primary
golden color with bluish-red background when viewed at 90~. The panels with PB 6 as
basecoat and the red to gold interference pigment in the topcoat have a primary color of
black with a golden interference color when viewed at 90~ and distinct polychromism.
Finishes with each of the following basecoaVclearcoat pigment combinations are obtained
by preparing the basecoat formulation according to Example 2, the tinted clearcoat
formulation according to Example 4A, and applying the finish according to Example 4B.
CA 02208119 1997-06-19
Tinted Basecoat
Clearcoat Pigment
Pigment
Greenish GoldPY 184
to Silver
Greenish GoldPY 110
to Silver
Greenish GoldPG 7 & TiO2
to Silver (50/50)
Greenish Gold PB 6
to Silver
Yellowish GoldPY 184
to Silver
Yellowish GoldPY 139
to Silver
Yellowish GoldPB 6
to Silver
Yellowish GoldPY 110
to Silver
Blue to Red PV 19
Blue to Red PB 6
Blue to RedPB 15.2 & TiO2
(50/50)
Red to Gold PV 19
Red to Gold PR 254
Red to Gold PB 6
Tinted clearcoats having a pigmenVbinder ratio of 0.0015/100, 0.015/100,1.5/100, and
5/100 and a thickness of about 50 ~lm are applied for each of the above-described
basecoaVclearcoat pigment combinations. In each instance, a finish showing polychromism
is obtained.
CA 02208119 1997-06-19
- 18-
Reflectance measurements are similar to those obtained with the three-coat systems
described in Example 3, as shown by the comparison of the reflectance measured at 25~
from the gloss angle of a panel with PB 6 in the basecoat and the Red to Gold opaque
interference pigment at a pigment to binder ratio of 1.5/100 in the midcoat (L=43.4, A=33.3,
B=43.2) or topcoat (L=44.4, A=33.3, B=42.9), or with PV 19 in the basecoat and the Red to
Gold opaque interference pigment at a pigment to binder ratio of 3/100 in the midcoat
(L=52.3, A=38.9, B=50.2) or topcoat (L=53.4, A=39.6, B=50.4) or with red iron oxide in the
basecoat and the Red to Gold opaque interference pigment at a pigment to binder ratio of
0.15/100 in the midcoat (L=30.4, A=31.8, B=32.6) ortopcoat (L=30.4, A=32.2, B=33.1).
By comparing the reflectance spectra of painted panels at various angles relative to the
gloss angle (90~ off the illumination source), it is observed that the relative reflection of the
inventive finishes is higher than would be expected on a proportional basis from the
reflectance of a panel covered to complete hiding with the opaque interference pigment as
the basecoat in a conventional basecoaVclearcoat automotive finish. Thus, a carbon black
pigmented basecoat overcoated with the red to gold interference pigment at a P/B ratio of
1.5/100 shows a % of maximum reflection at 650 nm and angles of 15~ and 25~ that is
respectively 384% and 368% relative to a panel covered with a conventional
basecoaVclearcoat automotive finish having a basecoat pigmented with the same
interference pigment at a P/B ratio of 15/100, whereas one would expect the reflectance to
be only about 10% on a strictly proportional basis.
This beneficial disparity is best observed with a black basecoat since the black basecoat
shows no color reflection. It is more difficult to measure the effect when a colored basecoat
is used since the basecoat also adds to the overall reflectance, but the advantage is still
apparent. Since quinacridone (PV 19) (RT-385-D from Ciba) does not reflect light at about
410 nm and the red to blue opaque interference pigment does, a comparison can be made
with this system. Thus, a basecoat of PV 19 overcoated as the second coating with a blue
to red opaque interference pigment at a P/B ratio of 1.5/100 demonstrates greater
reflectance than would be expected relative to the reflectance of a panel covered to
complete hiding at a P/B ratio of 15/100 with the same interference pigment and then
covered with a topcoat; the observed reflectance being 136% at 15~ and 161% at 25~
versus the expected 10%.
CA 02208ll9 l997-06-l9
-19-
Based on these observations, it is expected for a finish prepared according to the inventive
process to have a higher than proportional reflection at the reflection maxima relative to a
finish containing a hiding amount of the same interference pigment as the basecoat in a
conventional basecoat/clearcoat finish. However, this advantage may be more or less
difficult to measure depending on the coloristic properties of the basecoat and the opaque
interference pigment in the midcoat or topcoat.
