PURPOSE: To eliminate any strain on a projection picture due to oozing out of a coolant outside and curving of a translucent panel by making the volume of a coolant sealing space to be increased corresponding to a temperature rise of the coolant.

CONSTITUTION: Heat radiating metal structures 4 provided with so-called laminated bimetal parts 4c, in a flame-like form, wherein stainless steel parts 4a are lamellatedly joined with alloy parts 4b of iron and nickel, are arranged while being adhered together by adhesives 6 of a silicon system between the periphery of a phosphor screen panel 2 and the periphery of a translucent panel 3. And mixed liquid consisting of ethyleneglycol and water in the ratio of 4:1 is sealed in a space 5 as coolant. According to said constitution, the metal structures 4 curve with temperature rise and expand an interval between the phosphor screen panel 2 and the translucent panel 3 in the direction of the tube axis thus increasing a volume of the space 5 because coefficients of thermal expansion of the stainless steel parts 4a and the alloy parts 4b of iron and nickel composing the bimetal parts 4c of the metal structures 4 are different from each other accompanying the temperature rise of the coolant sealed in the space between both pannels 2 and 3.