Forming method of a pvb film for hud

A PVB film for HUD, wherein an accuracy error of HUD imaging achievable by the PVB film is ±0.1 mrad,

• wherein a cross section of the PVB film in one direction is wedged, and a cross section of the PVB film in another direction is curved, and
• wherein the PVB film is formed by a forming mold comprising an upper mold and a lower mold, the two of which can form an enclosed mold cavity when clamped together, wherein protective films are disposed on inner surfaces of the upper mold and the lower mold, respectively, for supporting PVB material and preventing the PVB material from bonding with the upper mold and the lower mold, and wherein shapes of the protective films match shapes of the upper mold and the lower mold,
• wherein the forming mold is a thermal-press forming mold that receives a PVB film therein as forming material to manufacture a formed PVB film for HUD imaging,
• wherein (a) a cross section of the mold cavity in one direction is wedged and a cross section of the mold cavity in another direction perpendicular to said one direction is curved such that the formed PVB film by the forming mold has a thickness that varies along said one direction and along said other direction, or (b) cross sections of the mold cavity in two directions, which are perpendicular to each other, are both curved such that the formed PVB film by the forming mold has a thickness that varies along each of said two directions, and
• wherein curved surfaces can compensate imaging accuracy based on a curved surface of a glass used by HUD imaging.