Machine learning methods have been widely used in the investigations of the
complex plasmas. In this paper, we demonstrate that the unsupervised
convolutional neural network can be applied to obtain the melting line in the
two-dimensional complex plasmas based on the Langevin dynamics simulation
results. The training samples do not need to be labeled. The resulting melting
line coincides with those obtained by the analysis of hexatic order parameter
and supervised machine learning method