Surface treatment method for composite surfaces

A surface treatment method for a composite surface of a basic casing, the composite surface cooperatively formed by an outer surface and four sidewalls surrounding the outer surface, the surface treatment method comprising:

• providing a heat transferring film;
• forming a printing pattern film on a portion of the heat transferring film via a digital inkjet printing process;
• and
• forming the heat transferring film on the composite surface via a vacuum heat transfer process, with edges of the heat transferring film being wrapped around the sidewalls and the printing pattern film being directly attached to the outer surface;
• wherein the printing pattern film comprises a basic layer, a printing pattern layer connected to a surface of the basic layer, and a second protective layer connected to a surface of the printing pattern layer facing away from the basic layer, the second protective layer is attached to the portion of the heat transferring film;
• wherein the heat transferring film comprises a heat pressing layer and a releasing film layer attached to a surface of the heat pressing layer;
• wherein the heat pressing layer comprises a glue layer, a pattern layer, and a first protective layer connected in that order;
• the releasing film layer is attached to a surface of the first protective layer away from the glue layer;
• wherein the second protective layer of the printing pattern film is attached to a surface of the glue layer facing away from the first protective layer.