Hot press with pressure vessels to uniformly distribute pressure to the work piece

A hot press used, for example, for producing a thin printed board and a multilayered board, such as liquid crystal glass board bonded by a low-viscosity adhesive, and to a hot press suitable for forming a board requiring uniform bonding pressure. A hot press includes an upper and a lower bolster arranged in vertically opposed relation to each other, an upper and a lower heat plate respectively disposed in opposed relation to the upper and lower bolsters, a device for moving at least one of the upper and lower bolsters toward the other to produce a pressing force between the upper and lower heat plates, and pressure vessels respectively mounted on the heat plates. Each pressure vessel is made of a thin film and is filled with a fluid heating medium. When substrate blanks are interposed between the upper and lower pressure vessels and pressed by them, surface pressure for adhesive bonding becomes uniform, and heat from the heat plates is uniformly transferred to the blanks.