A liquid crystal cell including antenna units includes a TFT substrate, a slot substrate, an acidic group-containing orientation film, a liquid crystal layer, and a sealant. The TFT substrate includes a first dielectric substrate, TFTs supported by the first dielectric substrate, and patch electrodes electrically connected to the TFTs. The slot substrate includes a second dielectric substrate and a slot electrode supported by the second dielectric substrate and including slots. The acidic group-containing orientation film on a surface of one of the TFT substrate and the slot substrate contains a polymer having an acidic group. The liquid crystal layer is interposed between the TFT substrate and the slot substrate in which the patch electrodes and the slot electrode are opposed to each other to constitute the antenna units. The sealant surrounds the liquid crystal layer and is interposed between the TFT substrate and the slot substrate.