Method for evaluating dispersion of material for light to heat conversion in thermal transfer film and thermal transfer film using the same

A method for evaluating dispersion of a light-to-heat conversion material in a thermal transfer film, the method comprising:

• calculating optical densities OD1 and OD2 of the thermal transfer film according to Equations 2 and 3, respectively;
• and
• calculating a dispersion evaluation value ΔOD according to Equation 1
• ΔOD=|OD2−OD1| Equation 1
• OD1=−log(T2/T1) Equation 2
• OD2=−log(T3/T1) Equation 3
• wherein T1 is transmittance of the thermal transfer film before placing the thermal transfer film in a transmittance measurement apparatus including a reflective mirror, T2 is transmittance of the thermal transfer film after placing the thermal transfer film in the transmittance measurement apparatus including the reflective mirror, and T3 is transmittance of the thermal transfer film after placing the thermal transfer film in the transmittance measurement apparatus without the reflective mirror, and
• wherein the thermal transfer film is determined to have satisfactory dispersion of the light-to-heat conversion material when the dispersion evaluation value ΔOD is 0.1 or less, and the thermal transfer film is determined to have unsatisfactory dispersion of the light-to-heat conversion material when the dispersion evaluation value ΔOD is greater than 0.1.