KR20000010980A - Gray primer optimizing method in laminated coating - Google Patents

Abstract

PURPOSE: A gray primer optimizing method is provided to repaint or refinish a vehicle and a truck by selecting a special primer paint composition applied before a top coat paint composition. CONSTITUTION: A gray primer optimizing method has the steps of: applying the coating layer of a primer composition; applying a top coating on a primer coating not to completely cover up the color of painted base material; applying laminated coating composition on the painted base material by performing color mixture of the top coating and already painted base material; the primer composition is each different a group of gray or white primer composition of 5¯ 20 numbers, is selected among groups mixed to be approached to the reflexibility of the top coat measured in minimum absorptive wave of the top coating.

Description

How to Optimize Gray Primer in Multi-Layer Coatings

The present invention relates to a method for repainting or refinishing automobiles and trucks by selecting a special primer paint composition applied prior to the top coat paint composition. In particular, the present invention relates to selecting a particular primer paint composition to be color blended with the original top coat when applying the top coat paint composition to a thickness that is less than the paint thickness required to completely conceal the substrate color.

In an effort to reduce the amount of top coat used to repair or repaint a car or truck body, the remaining portion of the vehicle that has not been repainted by applying it so as not to completely conceal the top coat when using a calibrated primer concentration. Since it is known that a top coat can still be obtained in combination with, techniques for selecting calibrated gray, white or black primers have been used. The cost is lowered by using smaller amounts of the top coating composition, while run, sag and popping can be lowered or eliminated while color formulation is still acceptable.

U.S. Pat. No. 4,546,007 (Abe et al., Oct. 8, 1985) shows that the spectral reflectance is as close as possible to the maximum value of the spectral reflectance curve of the top coat when the top coat is applied in full concealment. Or the method of selecting a black primer is used. The result of this method was found to be inaccurate about the color of the particular color tested. There is a need for a more accurate method of incorporating primers with top coats and essentially combining them with paint colors that are applied and repaired to a degree that does not completely hide the top coat.

Summary of the Invention

Original coating is applied by first applying a primer coating and then applying a top coating on the primer coating that does not completely conceal the color of the original painted substrate, thereby making the top coating the same color as the original painted substrate. The method of applying the multilayered coating composition on a coated substrate is characterized in that a gray or white primer coating is applied in a completely concealed state where the reflectance in the dry state is equal to the reflectance of the top coating measured at the minimum absorption wavelength of the top coating. do.

As used herein, the term "same as" means that as measured by human visual inspection, rather than by a colorimeter or spectrophotometer.

The method of the present invention is directed to a method of selecting a primer coat color that can be applied to a degree such that the top coating is not completely concealed on the primer, but can still be color blended with the original coated substrate. The method requires the use of primer coatings of varying gray concentrations and whites, including fairly dark grays and blacks. This is accomplished by combining the reflectance of the primer coat with the reflectance of the top coating. Reflectance is measured at the minimum absorption wavelength of the top coating. Use a primer whose reflectance is approximately equal to the reflectance at the minimum absorption wavelength described above.

The colored material reflects light of its own hue and absorbs light of other hue. Reflectance, or reflected light, is a measure of the light reflected by a surface at each wavelength. The present invention relates to the visible spectrum of light, i.e. about 400 to 700 nm. Reflectance for the primer coating as used herein is measured at the minimum absorption wavelength of the top coat. The minimum absorption wavelength is measured from light scattering theory, such as Kubelka-Munk theory. Primers whose reflectance is about the same as the reflectance of the top coating measured at the minimum absorption wavelength of the top coating are used in the method of the present invention.

The reflectance can be measured by a conventional spectrophotometer. Examples of commercially available spectrophotometers that can be used include Macbeth Color-Eye 3000 with an integral sphere measurement geometry; Bi-directional Bike-Gardner 9300 handy-spec spectrophotometer using 45/0 measurement geometry; And a bidirectional X-Rite MA-58 spectrophotometer using measurement geometries with aspecular angles of 25, 45 and 75 °.

Light scattering theory relates to the reflectance at each wavelength of color relative to the ability of the colorant to absorb or scatter light at the same wavelength. The most widely used theory is the one developed by Kubelka and Monk (see P. Kubelka and F. Munk, Ein Beitrag zur Optik der Farbanstriche, Z. tech. Physik., 12, 593, (1931)). Equation 1 is provided.

Where

K is the absorption coefficient,

S is the scattering coefficient,

R ₀ is the reflectance at the complete concealment.

By subtracting K and S at each wavelength of each colorant, K / S of the colorant mixture can be calculated by the following equations (2a) and (2b).

K _mixture = Σc _i K _i

S _mixture = Σc _i S _i

Where

c is the colorant concentration in the mixture,

i is the i-th colorant.

In addition, when the paint is applied to less than the complete concealment, the reflectance (R) can be calculated by the following equation (3).

Where

R _g is the reflectance of the substrate,

R ₀ is the reflectance of the complete concealment,

X is the film structure of the paint,

b is (1 / R ₀ -R ₀ ) / 2.

Samples of known composition and film structure were prepared on substrates of known reflectance to measure the reflectance of these samples, and K and S coefficients were calculated for each colorant at each wavelength by calculating K and S using the above equation. Can be measured. Typically, K and S are measured for one comparative colorant, such as aluminum flakes for metallic colors or white for non-metallic colors, and then a two-component blend is prepared with the comparative of each colorant to reflect the reflectance of these blends. And K and S for the remaining colorants are determined by calculating K and S using Equations 1, 2a and 2b. A more detailed discussion of K and S theory is in the literature (Color and Business, Science & Industry, Dean B. Judd and Gunter Wyszecki, John Wiley and Sons, Inc, (Second Ed., 1963)).

When repairing a vehicle, paint formulations for blending with existing colors can be inspected on a microfiche provided by a refinish paint supplier. The primer is then typically applied to the area to be repaired. The top coating should then be applied on the primer sufficient to completely conceal the primer to color blend with the unfinished finish of the vehicle. The present invention provides a method of selecting a primer color that can apply a thinner top coating thickness but still blend the color of the unrepaired surface.

By knowing the colorant concentration in the formulation for the blended top coating and pre-determining the K and S coefficients for each colorant, the K and S for the colorant mixture described above are calculated from Equations 2a and 2b at each wavelength. Typically these calculations are performed at intervals of 10 nm. Thus, we will calculate the K value to 31 and the S value to 31 on the visible spectrum. The wavelength whose K value is the lowest of these 31 values is the minimum absorption wavelength. The reflectance of the top coating at this wavelength is calculated by replacing the K and S values with Equation 1 at the same wavelength. Alternatively, the reflectance could be determined by spectrophotometer measuring the reflectance of the top coating in the fully concealed state at the wavelength. Subsequently, the selected gray primer could have a reflectance at the wavelength equal to or substantially close to the reflectance.

The primers could be obtained by several routes. One method is to use black primers and white primers, blending them in a ratio that provides the reflectance. The ratio could be achieved by trial and error until the correct reflectance was obtained. In addition, since the K and S values of these primers are known, when calculating the concentrations in Equations 2a and 2b, the ratio can be determined by computer so that Equation 1 provides accurate reflectance. Another method is to have several (5 to 20) light incremental primers whose spectral reflectance on the visible spectrum is predetermined by measurement or calculation. Once the top coating reflectance at the minimum absorption is known, the optimal primer can be selected by finding a primer of reflectance close to the reflectance at the same wavelength. If only five primers were used, intermediate primers could be prepared by blending a bicomponent mixture of these five primers in a known ratio to provide spectral reflectance.

The following examples illustrate the invention. All percentages are based on weight.

The metallic orange top coating paint was sprayed in full concealment. The concealed state was determined by placing checkered black and white concealed tabs at one corner of the panel. The top coat shields the black and white squares when applying the top coating. When applying a top coating sufficient to conceal, the naked eye cannot perceive any top coat color difference on the black and white squares. Reading through the instrument gives the same spectral curve when measured over white and black respectively. The measured spectral reflectance curves are shown in FIG. 1 (the curves labeled H for “Hiding”). Three gray primers were considered for the undercoat. Their reflectance curves are also shown as P ₁ , P ₂ and P ₃ in FIG. ₁ . US Pat. No. 4,546,007 (Abe et al.) Teaches the use of primers whose spectra reflectance is as close as possible to the maximum value of the spectral reflectance curve of the top coat in a fully concealed state. The maximum reflectance in the concealed state of the top coating occurs at 700 nm and the primer that most closely combines the reflectance at that wavelength is the P ₁ primer as shown in FIG. ₁ .

The method of the present invention indicates that the P ₁ primer is not color best blended. Using the Kubelka-Munk theory, it was determined that the minimum absorption wavelength of the top coating was 580 nm, shown as "A" on FIG. 1. The absorption at this wavelength using Equation 2a was calculated at 1.14, but the absorption at peak reflectance (700 nm) was calculated at 4.81. The reflectance of curve H at 580 nm was 11.1%. The primer whose reflectance at 580 nm is close to 11.1% is P ₂ (primer 2); The next choice is P ₃ (primer 3). When the orange top coat was sprayed onto these three primers applying only four coats of the top coat, the resulting spectral curves are shown as P ′ ₁ , P ′ ₂ and P ′ ₃ in FIG. 1. The top coating curve on P ' ₂ (primer 2) is closest to the curve H of the top coating in the concealed state, where P' ₂ (primer 2) as selected by the method of the present invention is a method of the prior art of Abe patent. Rather than primer 1, which was the determined primer.

Claims (7)

The coating layer of the primer composition is first applied, and then the top coating is applied to the primer coating to a degree that does not completely conceal the color of the painted substrate, thereby performing color formulation of the top coating and the already painted substrate. A method of applying a multilayer coating composition on a substrate, wherein the gray or white primer composition is applied in a completely concealed state where the reflectance in the dry state is essentially the same as the reflectance of the top coating measured at the minimum absorption wavelength of the top coating. How to improve that. The primer composition of claim 1, wherein the primer composition is about 5 to 20 groups of gray or white primer compositions each having a different brightness and selected from the group that is most closely formulated to the reflectance of the top coat measured at the minimum absorption wavelength of the top coating. How to be. The method of claim 1, wherein the reflectance measurement at the minimum absorption wavelength is determined by measuring the reflectance of the top coating at this wavelength. The method of claim 2 wherein the reflectance is formulated at ± 20%. The method of claim 1, wherein the reflectance of the top coating at the minimum absorption wavelength is calculated using Kubelka-Munk calculation. The method of claim 2, which is measured using a spectrophotometer using an integral sphere geometry. The method of claim 6, which is measured using a spectrophotometer using bidirectional geometry.