  We investigate the escape process from a perpendicular shock region of a
spherical shock in the interstellar medium (ISM). The diffusive shock
acceleration in the perpendicular shock of supernova remnants (SNRs) has been
expected to accelerate cosmic rays (CRs) to the PeV scale without an upstream
magnetic field amplification. We estimate the maximum energy of CRs limited by
the escape from the perpendicular shock region. By performing test particle
simulations, we confirm the theoretical estimation, showing that the
escape-limited maximum energy in the perpendicular shock is several 10 TeV for
the typical type Ia SNRs. Therefore, in order for SNRs in the ISM to accelerate
CRs to the PeV scale, an upstream magnetic field amplification is needed. The
characteristic energy scale of several 10 TeV could be the origin of the
spectral break around 10 TeV, which was reported by recent direct CR
observations. In addition, we show that, in the free expansion phase, the rapid
perpendicular shock acceleration works on about 20% area of the whole shock
surface, which is larger than the size of the superluminal shock region. We
also discuss the escape of CR electrons from the perpendicular shock.
