Patent ID: 8035670

Claim:
A thermal transfer sheet comprising: a substrate, and a plurality of coloring material layer units disposed on one surface of the substrate in a plane sequential manner, each of the coloring material layer units including at least two types of coloring material layers arranged parallel to each other, the coloring material layers containing coloring materials, wherein the coloring materials are thermally transferred onto an image-receiving layer of a thermal transfer-receiving sheet superimposed with the thermal transfer sheet to form transferred images, the transferred images formed by the coloring material layers in each coloring material unit have a value C defined by mathematical formula 1 below of less than 12, and colorimetric values P (a*, b*) of the transferred images defined by mathematical formulae 2 and 3 below are different from one another within each coloring material unit: C =([ a*] 2 +[b*] 2 ) 0.5 (mathematical formula 1) where C represents chroma and a* and b* each represent a colorimetric value (CIE 1976 L*a*b* color space with D65 illuminant, 2° field of view) equivalent to L*=38; [ a *]=( ay−ax )/( Ly−Lx )*(38− Lx )+ ax (mathematical formula 2) [ b *]=( by−bx )/( Ly−Lx )*(38− Lx )+ bx (mathematical formula 3) where Lx, ax, bx, Ly, ay, and by represent colorimetric values at adjacent step Sx and step Sy near L*=38 when stairstep images are formed by transfer on the image-receiving layer of the thermal transfer-receiving sheet by using the coloring material layers; and Colorimetric values (L*, a*, b*) at step Sx=(Lx, ax, bx) Colorimetric values (L*, a*, b*) at step Sy=(Ly, ay, by) where Lx<38<Ly or Lx>38>Ly.