The influence of bending waves on the warm-up behavior of exciton absorption bands in layer crystals had been investigated. The effective mass of the current carriers in the layer semiconductor Pb12 has been computed and used to obtain the values of the exciton-phonon interaction function by pseudopotential method energy spectra calculations. It was shown that the different signs of the warm-up dynamics of an exciton absorptions peak shift and existence of inversion p oints i 5 related with t he c oncurrent i nfluence o f t wo e xciton e nergy r elaxation mechanisms -o n b oth t he bending waves and the lattice phonons.