MASK PROTECTING DEVICE

摘要

In a mask protective device comprising a frame, the size of which is set to surround a mask pattern, and a transparent thin film 12 spread and fixed to the frame to close one opening of the frame, the periphery of the transparent thin film 12 is bonded to an end face 11a at one opening of the frame 11 by adhesives 41 applied on the whole surface of the end face 11a to cover and close the opening of the frame 11. A string-like bead 42 is formed on an end face 11b at the other end opening of the frame 11 by linearly applying adhesives, for bonding the frame 11 to the mask 17, all around the end face 11b of the frame 11. The string-like bead 42 formed on the end face 11b at the other opening of the frame 11 can be formed helically, formed in two lines arranged inside and outside in parallel with each other which have respective discontinuities at different places to have openings allowing the communication between the inside and the outside the mask protective device, or the like. As the mask protective device 40 is mounted on the mask 17 and bonded to the mask 17 by the string-like bead 42 made of adhesives linearly applied to the end face 11b of the frame, the top of a curved groove of which side walls are portions of the string-like bead 42 is closed by the mask 17, the groove becomes an air passage 43 allowing the communication between the inside and the outside of the frame 11. Therefore, the inner space 19 of the mask protective device 40 communicates with the outside through the air passage 43 so that air in the mask protective device 40 moves in and out through the air passage 43 even with changes in atmospheric pressure and/or in temperature, thereby preventing the thin film 12 from swelling or denting and preventing the damage of the thin film 12 and trouble on the optical characteristics. <IMAGE>