An adhesive for a flexible optical film, especially an acrylate pressure-sensitive adhesive for a flexible display device is disclosed. The shear storage modulus (G′(60° C./0.1 Hz)) at the temperature of 60° C. and the frequency of 0.1 Hz and the shear storage modulus (G′(30° C./1 Hz)) at the temperature of 30° C. and the frequency of 1 Hz of the present acrylate pressure-sensitive adhesive satisfy the relation: (G′(60° C./0.1 Hz)−G′(30° C./1 Hz))/G′(30° C./1 Hz)>−0.29, and the loss tangent (tan δ(60° C./0.1 Hz)) at the temperature of 60° C. and the frequency of 0.1 Hz and the loss tangent (tan δ(30° C./1 Hz)) at the temperature of 30° C. and the frequency of 1 Hz of the present acrylate pressure-sensitive adhesive satisfy the relation: (tan δ(60° C./0.1 Hz)−tan δ(30° C./1 Hz))/tan δ(30° C./1 Hz)