US Patent 10933681 Secure substrate

A secure substrate may include a base layer and an opacity layer disposed above the base layer. An optional background layer may be disposed above the opacity layer. The secure substrate may further include an inkjet receptive layer. A first inkjet receptive layer may be disposed above the background layer, and a second inkjet layer may be disposed below the base layer. The opacity layer may include copper such as metallic copper flakes or other particles. The opacity layer may also include a binder material such as polyvinyl alcohol, and in some cases also carbon black, process black, or the like.