A method for producing a three-dimensional decorative piece of a thermoplastic synthetic resin by subjecting a decorative piece material to high-frequency dielectric heating, wherein the decorative piece material comprises
- a lower layer of a thermal bonding film,
- an intermediate layer of a thermoplastic synthetic resin sheet wherein the intermediate layer is stacked on the lower layer, and
- an upper layer of a thermoplastic synthetic resin film wherein the upper layer is provided on a lower side thereof with a vapor-deposited metal layer and is stacked on the intermediate layer,
- the upper layer including a first printing layer and a second printing layer, wherein the first printing layer is formed on an upper surface of the upper layer by screen printing thereon a transparent color ink, a matte ink, or a glossy ink, and the second printing layer is formed on an upper surface of the first printing layer by screen printing thereon a fine line using a transparent UV ink, wherein the second printing layer is cured by irradiated ultraviolet rays such that the fine line has a thickness and is provided on an upper surface thereof with an adhesive carrier film,
- the method comprising:
- a placing step of placing the decorative piece material on top of a table to be served as one electrode during high-frequency dielectric heating;
- a first high-frequency dielectric heating step including pressing an engraved die against the upper layer of the decorative piece material wherein the engraved die is served as another electrode during high-frequency dielectric heating, and performing high-frequency dielectric heating for the decorative piece material whereby the upper layer of the decorative layer is bulged into a protruded form having a three-dimensional design, a portion other than the carrier film is fusion-cut with an outer contour line of the engraved die, the upper layer is fused with the intermediate layer, and the intermediate layer is fused with the lower layer,
- a removing step of removing an unnecessary portion that does not constitute the three-dimensional design in the fusion-cut decorative piece material;
- a second high-frequency dielectric heating step including positioning the decorative piece material into the engraved die placed on the table with an engraved surface facing upward such that the three-dimensional design of the decorative piece material fits into the engraved surface of the engraved die, placing a base material on the decorative piece material, pressing the base material against the decorative piece material using a flat-plate die from above the base material, and performing high-frequency dielectric heating to weld the base material and the decorative piece material to each other;
- and
- an adjustment step including bringing out the welded decorative piece material and base material from the engraved die, peeling off the carrier film, and cutting the base material to a desired shape to obtain the three-dimensional decorative piece of a thermoplastic resin.