Patent ID: 8557361

Claim:
An optical data storage medium comprising: (A) a laminar plastic disc having first and second opposed surfaces, said plastic disc comprising at least one data-storing layer, and (B) a color-forming composition overlying said first surface, said color-forming composition comprising, in order of increasing distance from said first surface: (B)(1) a first color-forming layer; (B)(2) a first thermally-insulating layer; (B)(3) a second color-forming layer; (B)(4) a second thermally-insulating layer; and (B)(5) a third color-forming layer; wherein said color-forming layers are initially colorless and form a color when heated; wherein the color-forming temperature of said first color-forming layer is lower than the color-forming temperature of said second color-forming layer, and the color-forming temperature of said second color-forming layer is lower than the color-forming temperature of said third color-forming layer; and wherein the color forming composition is configured to maintain a change in radial tilt of said optical disc measured at any location of less than 0.6 degrees when the ambient humidity changes from 75% RH to 10% RH at a constant temperature between 20° C. and 30° C.