Langmuir-Blodgett films of several 1:2 charge-transfer complexes of azobenzene-containing alkylpyridinium and tetracyanoquinodimethane (TCNQ), which exhibit various conductivity-change phenomena upon UV and visible light irradiation, have been investigated by using the ESR technique. The in-situ illumination measurements of these films and the quantitative analyses of the obtained spectrum show the changes in the exchange couplings between the spins and suggest the structural change in the TCNQ columns. By adopting the one-dimensional Hubbard model with dimerization effect, we propose a conductivity-change mechanism in the system.