Liquid crystal aligning agent, polyorganosiloxane, liquid crystal aligning film, forming method thereof and liquid crystal display element

The present invention relates to a liquid crystal aligning agent, polyorganosiloxane, a liquid crystal aligning film, a forming method thereof and a liquid crystal display element. The present invention provides the liquid crystal aligning agent which can form the liquid crystal aligning film that can generate a pretilt angle with long time stability through an optical aligning method. The liquid crystal aligning agent comprises radiation-sensitive linear polyorganosiloxane which is prepared through the reaction of the following components: specific polyorgansiloxane with epoxy radical; (A) cinnamic acid derivative; and (B) a specific compound with a radiation-sensitive structure that is preferably selected from: acetophenone structure, benzophenone structure, anthraquinone structure, biphenyl structure, carbazole structure, nitro-aryl structure, fluorenes structure, naphthalene structure, anthracene structure, acridine structure and indole structure.