Study On The Spot Color Matching Of Offset Ink

The computer ink color matching has developed rapidly in the recent years, but the precision and cost can not meet people's demand. The purpose is studying the spot color matching of the offset ink by synthesizing tri-stimulus and spectrophotometric color matching, improving color matching precision, keeping the manuscript's fidelity, reducing cost, saving the energy and offering theory and technology basis for computer ink color matching.The dot area of the Neugebauer Equation was modified with the dot-gain modified method according to printing chromatology and theory of ink. The"tri-stimulus and spectrophotometric color matching"was put forward based on mean square variance minimum theory, tri-stimulus and spectrophotometric color matching method. The color matching software was compiled with VC++6.0.The data were handled with the least squares and correlation coefficient method. The ink formulation was evaluated using color difference and metamerism index.The L*, a* and b* values of K+E chromatogram samples were measured by densimeter. The edge points in the chromaticity coordinates were linked to form color gamut of six color areas. The dot area for the Neugebauer Equation at each color area was corrected, and revised exponents were obtained. The proofs'chromatic values were calculated using modified Neugebauer Equation. The precision of modified Neugebauer Equation was proved by comparing measuring values with calculating values. The software was compiled according to"tri-stimulus and spectrophotometric color matching". The model between thickness and quantity of ink was established by printability tester proofing. The relation between dot area and chromatic values was analyzed. The formulation was calculated according to spectrum reflectance of color samples and software. The experiment was done by printability tester and experimental result was evaluated.It has indicated: The average color difference of proofs between measuring chromatic values and calculating chromatic values using modified Neugebauer Equation is less than 3. The ink thickness increases along with ink quantities, and the relationship between ink thickness and quantity is of conic. The curves of dot area and chromatic values are also conics. Using"tri-stimulus and spectrophotometric color matching", the experiment samples done by IGT show that the average color difference is 2.02, and metamerism index is 1.79. The precisions are increased 32.67% and 40.33% separately.