A security display apparatus is provided including an image processor which reverses a normal image to create a reverse image which is a negative of the normal image, and a display unit which displays the normal image and the reverse image. According to this, bubbles in the coating liquid can reliably be removed irrespective of the nature of the coating liquid, a large amount of coating liquid can be treated, and the possibility that the quality of the deaerated coating liquid is adversely affected is eliminated. License status data is transmitted with or without content from one consumer to another. The solenoid plunger may be coupled to a quick-release lock. The density of thermoelectric composition ranges from about 80% to about 100% of theoretical density.