Information recording medium
An information recording medium having a front surface and a back surface has a first color developing layer, a second color developing layer and a third color developing layer. The first color developing layer develops yellow at a temperature not less than a first threshold value. The second color developing layer is arranged at the back surface side with respect to the first color developing layer. The second color developing layer develops magenta at a temperature not less than a second threshold value that is lower than the first threshold value. The third color developing layer is arranged at the front surface side with respect to the first color developing layer. The third color develops cyan at a temperature not less than a third threshold value that is higher than the first threshold value.
1. An information recording medium to be used for an identification card having a front surface and a back surface comprising:
a first color developing layer which has a minimum value of a spectral reflectivity at a first wavelength, and develops a first color at a temperature not less than a first threshold value;
a second color developing layer which is arranged at the back surface side with respect to the first color developing layer, has a minimum value of a spectral reflectivity at a second wavelength that is longer than the first wavelength, and develops a second color at a temperature not less than a second threshold value that is lower than the first threshold value; and
a third color developing layer which is arranged at the front surface side with respect to the first color developing layer, has a minimum value of a spectral reflectivity at a third wavelength that is longer than the second wavelength, and develops a third color at a temperature not less than a third threshold value that is higher than the first threshold value.
2. The information recording medium to be used for an identification card according to claim 1 wherein:
the first color is yellow;
the second color is magenta; and
the third color is cyan.
3. The information recording medium to be used for an identification card according to claim 2 wherein:
the third threshold value is 300° C.;
the first threshold value is 200° C.; and
the second threshold value is 150° C.
4. The information recording medium to be used for an identification card according to claim 2 further comprising:
a first spacer layer arranged between the first color developing layer and the second color developing layer;
a second spacer layer arranged between the first color developing layer and the third color developing layer; and
a protective layer arranged at the front surface side with respect to the third color developing layer;
wherein a thickness of the first spacer layer is thinner than a thickness from a surface at the back surface side of the first color developing layer to a surface at the front surface side of the protective layer.
5. The information recording medium to be used for an identification card according to claim 4 further comprising:
a third spacer layer which is arranged between the third color developing layer and the protective layer.
6. The information recording medium to be used for an identification card according to claim 1 wherein:
the third color developing layer contains a pigment expressed by a chemical formula described below: