  We report results of a systematic analysis of spatial solitons in the model
of 1D photonic crystals, built as a periodic lattice of waveguiding channels,
of width D, separated by empty channels of width L-D. The system is
characterized by its structural "duty cycle", DC = D/L. In the case of the
self-defocusing (SDF) intrinsic nonlinearity in the channels, one can predict
new effects caused by competition between the linear trapping potential and the
effective nonlinear repulsive one. Several species of solitons are found in the
first two finite bandgaps of the SDF model, as well as a family of fundamental
solitons in the semi-infinite gap of the system with the self-focusing
nonlinearity. At moderate values of DC (such as 0.50), both fundamental and
higher-order solitons populating the second bandgap of the SDF model suffer
destabilization with the increase of the total power. Passing the
destabilization point, the solitons assume a flat-top shape, while the shape of
unstable solitons gets inverted, with local maxima appearing in empty layers.
In the model with narrow channels (around DC =0.25), fundamental and
higher-order solitons exist only in the first finite bandgap, where they are
stable, despite the fact that they also feature the inverted shape.
