the ventilation hole 41 on the chassis bed 40 are provided as examples for describing the pdp of embodiments of the present invention and if the air in the sealed space or open space between the chassis bed and the chassis base can flow sufficiently toward the upper surface of the chassis base the chassis bed and the arrangement of the ventilation hole can be variously modified referring to fig4 a and 5 b the pdp of the present embodiment is the same as that of fig3 except for a third ventilation hole 55 is formed on the circuit board 50 such as the buffer board that is the air heated by the circuit device 46 flows toward the upper portion of the chassis base 30 through the space between the circuit board 50 and the chassis base 30 and can flow while penetrating the circuit board 50 through the third ventilation hole 55 formed on the circuit board 50 and thus the heat generated by the circuit board 46 can be effectively dissipated in fig5 b the end portion of the chassis base 30 is not bent and the other elements are the same as those of fig5 a the difference between the panels of fig5 a and fig5 b can refer to the descriptions of fig3 a and 3b in the pdp including the chassis bed 40 having the ventilation holes 31 41 and 55 and the circuit board 50 the air heated by the circuit device 46 such as the tcp ic can sufficiently flow through the ventilation holes 31 41 and 55 and thus the heat dissipation of the circuit device 46 can be accelerated.