a back panel, comprising a base plate and a vertical plate connected with an edge of the base plate, wherein the base plate is matched with the vertical plate to form an accommodation space;

a light guide plate, located in the accommodation space and having a safety gap with the vertical plate of the back panel;

an optical film, located in the accommodation space and located on a side of the light guide plate away from the base plate;

wherein a surface of the light guide plate facing the optical film has a first positioning portion and a second positioning portion, the first positioning portion positions the optical film in a first direction, the second positioning portion positions the optical film in a second direction, and the first direction and the second direction are perpendicular to each other and both parallel to an extending surface of the light guide plate;

the first positioning portion comprises at least one pair of positioning bosses arranged in the second direction; the second positioning portion comprises at least one pair of positioning bosses arranged in the first direction; the optical film is located in an area defined by the first positioning portion and the second positioning portion, and an edge of the optical film has avoidance notches in one-to-one correspondence with the positioning bosses; and the positioning bosses are cooperatively inserted into the corresponding avoidance notches;

an edge of a side of the optical film facing the surface of the light guide plate is fixedly bonded to the light guide plate;

a gap is provided between a sidewall of the avoidance notch in the optical film and a sidewall of the positioning boss.