Patent ID: 7925468

Claim:
A method of characterizing hiding of a coating composition, said method comprising: (i) applying a monotonic layer of said coating composition over a test pattern affixed to a hiding test panel to produce a monotonic coating thereon; (ii) sequentially uniformly illuminating target areas P 1 to P n of said monotonic coating, each said target area comprising a light portion and a dark portion; (iii) sequentially directing reflections of said target areas P 1 to P n to a photosensitive device for acquiring: (a) intensities lr 1 to lr n , lg 1 to lg n and lb 1 to lb n of said light portions of said areas P 1 to P n , and (b) intensities dr 1 to dr n , dg 1 to dg n and db 1 to db n of said dark portions said areas P 1 to P n ; (iv) sequentially measuring applied measured thicknesses X 1 to X n of said monotonic coating at locations that respectively correspond to said target areas P 1 to P n ; (v) sequentially computing measured Y 1 to Y n at said target areas P 1 to P n by using the formula: [(lr i −dr i ) 2 +(lg i −dg i ) 2 +(lb i −db i ) 2 ] 0.5 (1) wherein i ranges from 1 to n, and said measured Y 1 to Y n are measured ΔRGBs; (vi) storing on a computing device hiding data comprising said measured Y 1 to Y n and said applied thicknesses X 1 to X n ; (vii) determining a threshold measured Y th by using the formula: measured Y th =Log e (measured Y max ), (2) said measured Y max being the maximum value within the range of said measured Y 1 to Y n ; (viii) sequentially comparing said measured Y 1 through Y n to identify first measured Y q that is less than measured Y th wherein q falls within said range 1 to n; (ix) computing a ratio (q/n) to classify said hiding data, wherein said is classified as: (i) type 1 hiding data when said ratio is in the range of 0.01 to less than 0.25, (j) type 2 hiding data when said ratio is in the range of 0.25 to less 0.35, (k) type 3 hiding data when said ratio is in the range of 0.35 to less 0.50, or (l) type 4 hiding data when said ratio is in the range of 0.50 to 1.00; (x) selecting one or more fitting equations applicable for said type 1 hiding data, type 2 hiding data, type 3 hiding data or type 4 hiding data, wherein said fitting equations define a relationship between (y) and (x), said (y) being a fitted color difference that corresponds to said (x), which is a fitted thickness on a fitted curve generated by said one or more fitting equations; (xi) fitting said one or more selected fitting equations to match paired measured (X 1 , Y 1 ) to paired measured (X n , Y n ), wherein said fitted curve has a fitted baseline value of y b at an asymptote of said fitted curve; (xii) selecting a fitted threshold value y th above said fitted baseline value y b , wherein said fitted threshold value y th is suited for said type 1 hiding data, type 2 hiding data, type 3 hiding data or type 4 hiding data; and (xiii) locating a hiding thickness x h of said coating composition that corresponds to said fitted threshold value y th on said fitted curve.