a metal layer; and

a film layer to hold the metal layer comprising a film to hold the metal layer, wherein the film holds the metal layer, wherein the film to hold the metal layer comprises: a thermoplastic resin that is a modified polyethylene terephthalate resin having a melting point of 235° C. to 243° C., wherein the film to hold the metal layer has transparency,

a second adhesive layer including one resin or a mixture of two or more resins selected from polyurethane-based, polyvinyl acetate-based, ethylene vinyl acetate copolymer-based, epoxy-based, and silicone-based resins,

wherein the metal layer, the film layer to hold the metal layer and the second adhesive layer are laminated in sequence, and

wherein the thickness of the metal layer is 10 nm to 100 nm, and

wherein the metal layer has a sea-island structure in which islands of metal particle have gaps apart from each other,

wherein the metal layer is vacuum-deposited on one side of the film layer to hold the metal layer,

wherein the film to hold the metal layer is a film that is softened and drawn down by heating, and wherein a temperature difference between a temperature at which the film to hold the metal layer recovers from drawdown and a temperature at which the film to hold the metal layer starts to hang down due to melting is from 95° C. to 120° C.,

wherein the temperature difference is determined for the film to hold the metal layer by performing a clamping step and a heating step and then measuring changes in a surface temperature of the film to hold the metal layer and the hanging state of the film to hold the metal layer,

wherein the clamping step includes cutting the film to hold the metal layer into 350 mm×300 mm, and the film to hold the metal layer is sandwiched from above and below by a clamping frame of a vacuum-compressed air forming machine, and four sides of the film to hold the metal layer is gripped so as not to cause loosening by their own weight,

wherein the heating step is performed after the clamping step, the film to hold the metal layer is moved to a heating section of the vacuum-compressed air forming machine, and heaters each having nine heat generating bodies are arranged above and below the film to hold the metal layer, and then the film to hold the metal layer is heated uniformly, and wherein

during the heating step, the film to hold the metal layer is observed in a horizontal direction to evaluate the behavior of hanging of the sheet due to heating.